The invention relates to a development of a special circuit arrangement for triggering a vehicle passenger protection system and previously disclosed per se by DE-A-2,309,111, FIG. 3. In this prior art, a parallel circuit of two current branches each having a dedicated trigger and dedicated capacitor as well as a dedicated individual triggering switch is provided, as is a common triggering switch connected in series to the triggers, it being the case that, when seen from a voltage source feeding the current branches, the capacitor is connected, as it is being charged, in each case in parallel to the assigned trigger. In the event of an accident, the capacitors generate powerful current impulses through the assigned triggers. Before the accident, the triggers are connected to floating potentials, that is to say not to defined continuous-operation voltages. Nothing is specified concerning sporadic or continuous checks of the serviceability of the most important parts of the circuit arrangement, for example its capacitors.
In the circuit arrangement according to the invention, as they are being charged the capacitors are not connected in parallel but in series to the assigned triggers. Moreover, in the invention not only the capacitors, but also the triggers are connected to definable continuous-operation voltages, it being the case that, at least in principle, the amounts of these continuous-operation voltages before the accident are sufficient to permit a certain indication of serviceability, of the primer capsule as well, because unusual continuous-operation voltages point to disturbances.
A plurality of triggering switches are also provided in the circuit arrangement described in EP-A1-0,284,728, to be precise both in series with respect to the parallel circuit, and in each case an additional dedicated triggering switch in each current branch in series with respect to the capacitor. In the event of an accident, these capacitors permit the flow of the current impulse in the relevant current branch only until this capacitor has been charged by this current flow. However, these capacitors serve not to store the energies required for triggering, but expressly the purpose of avoiding a complete discharge of an additional ignition capacitor, centrally provided there, as early as during the ignition of a first one of the primer capsules, in order for the ignition of the remaining primer capsules to be ensured as well. In addition, it follows from the figure of the abovementioned prior art that before the accident the relevant capacitors are not connected during the journey to any voltage source, that is to say are not charged to a reliably definable continuous-operation voltage. Moreover, the relevant capacitors of the current branches have in each case only approximately 20% of the capacitance of the ignition capacitor centrally provided there. Thus, in the known circuit arrangement it is really only the centrally provided ignition capacitor which before the accident stores the energy required to trigger the triggers. The capacitors provided in the known circuit arrangement thus do not store sufficient energy before the accident to be able in the event of an accident to trigger the trigger located in their current branch.